1. Field of the Invention
This invention relates to a having a zooming function.
2. Description of the Related Art
Conventional lens moving apparatus of the type which employs a plate cam have been proposed in British Patent No. 937,245, Japanese Utility Model Publication No. Sho 39-13162, U.S. Pat. Nos. 3,181,447 and 3,533,344, Japanese Patent Publication No. Sho 46-13110, Japanese Laid-Open Patent Application Nos. Sho 59-104613, Sho 59-192212, Sho 60-91311, Sho 59-176711, Sho 62-139510, Sho 60-216319, Sho 60-216320, Sho 60-87310, Sho 59-176712, Sho 59-192214 and Sho 59-192213.
Conventionally, a cylindrical cam tube is used for the movement of a zoom lens. However, the cylindrical cam tube requires a high dimension accuracy and a long processing time, and is therefore expensive. Accordingly, it has been proposed to make a cam a flat component and manufacture it by pressing at a low cost. Several types of plate cams are known. However, none of them has been put into practical use. Movement of a zoom lens requires movement of at least two lens groups. In consequence, in the case of a zoom lens in practical use, drive of all the lens groups by means of the plate cam increases the area of the plate cam and, hence, the size of the lens barrel. When lenses have a cylindrical configuration, the size of the lens barrel is particularly increased.
In a case where zooming is electrically operated using the plate cam, when an actuator for driving lenses, a gear train, a driving circuit and so on are disposed within the cylindrical lens barrel, the size of the lens barrel is increased.